DAP Products plugs large cracks and holes with its Caulk Backer Rod to save caulk and prevent joint failure in foundations, walls, pavement, and windows and doors. Applicable with almost any type of caulk or sealant, the flexible, closed-cell polyethylene foam rod wedges into joints and keeps them air- and water-tight, the company says. The 1/2-inch-thick backer rod comes in 20-foot rolls. 410.675.2100. www.dap.com.